1. Field of the Invention
The present invention relates to a water-swelling composition. In particular, it relates to a water-swelling composition usable for places which must be water or moisture tight in vehicles, buildings, various machines, and the like.
2. Description of the Related Art
In vehicles, buildings, machines, etc., places which must be water or moisture tight are filled with a sealant for the purpose of preventing the penetration therefrom of water and moisture.
Among sealants known in the prior art, there are water-swelling sealants which are consisted of a polymeric base (mainly a rubber) and a water-swelling polymer, such as starch and a polyacrylate.
When a sealant is used for a long period of time in vehicles, buildings, machines, etc., gaps or hiatuses may be formed at sealed places because of its deterioration and/or contraction caused by the influence of ultraviolet rays, heat or the like, or because of deformation of vehicles, buildings, machines, etc. As a result, its sealing function tends to be lowered with the lapse of time. However, when contacted with water or moisture, a water-absorbing polymer contained therein swells to increase the bulk of the sealant. As a result, gaps or hiatuses formed in sealed places can be filled up automatically and, hence, the sealing function of a water-swelling sealant can be maintained over an extended period of time.
However, a long period of time up to, e.g., one week, is required for the completion of such a swelling since a rubber, the base material of such a sealant, is an inherently hydrophobic substance and incompatible with water.
Such a water-swelling sealant may, therefore, be of no use when a speedy swelling is required as in the case of a rainfall. Because of this reason, water-swelling sealants have been employed only for uses where rapid protection against water is not required.